Tach Problem with 911 SC Engine Transplant

[JimSuke]

Hi all,

I've acquired a 1968 912 with a SC 3.0 transplanted into it. The tach has been changed to a 911S tach and does not work. The previous owner indicated that he hasn't had a tach working in the car since the transplant.

There is an older Perma Tune module present and seems to be working fine. It has the lead for a tach signal. The wiring checks out.

I believe I need to either get a SC tach or and intermediate switch (?).

Any guidance would be very appreciated.

Jim

[Flat6pac]

Open the 14 prong connector off the engine. with the cap off, the first wire in on the top is purple/black, thats your tach wire. Jump it to a purple / black off the chassis in the left rear area and your tach should drive.
Bruce

[JimSuke]

Thanks for the reply Bruce but I don't have a 14 prong connector but a 6 which connects to the Perma-Tune unit. The 6 prong connector has a purple and black wire which I've connected the tach to with no luck.

My problem is that the signal coming from the Perma-Tune is not compatible with the 911s tach in the car. This tach is looking for a signal from the coil but, according to the info I found on the Perma-Tune, this could damage the unit ($500 replacement).

Any ideas?

Thanks again

[john walker's workshop]

send it to north hollywood speedometer and tell them what you have, or find an SC tach.